This invention relates to a floor cutter bit for a mineral winning machine, and in particular to a floor cutter bit for a coal plough.
A coal plough floor cutter bit typically has cutting edges formed respectively on a pair of cutter plates, which are made of hard, wear-resistant metal, and which are positioned against one another to form an L-shape. One of the cutter plates (the floor cutter plate) is generally horizontal and positioned at the base of the body of the floor cutter bit; and the other cutter plate (the coal-face cutter plate) extends upwardly relative to the floor cutter plate. The two cutter plates are soldered into apertures in the body of the floor cutter bit. The cutting edge of the floor cutter plate extends obliquely upwards in the direction towards the coal face to be won. This configuration of the floor cutter plate results in the floor cutter bit cutting out a furrow in the floor of a mine working, which furrow also has a floor which slopes upwardly towards the coal-face. These sloping furrow floors facilitate the advance of the conveyor along which the coal plough is reciprocated to win the coal. This is because the leading edge of the conveyor (or of the plough guide attached thereto) engages within the furrow; and, because of the upward slope of the furrow, is subjected to only slight resistance during conveyor advance. Unfortunately, because of its upwardly-inclined cutting edge, the entire length of the floor cutter plate participates in the winning work, so that the floor cutter plate is heavily loaded, particularly where the floor cutter bit cuts into rock in the floor of the mine working (which is unavoidable in most mining operations). (see DE-Gm 75 06653).
This known type of floor cutter bit thus has a rather short working life because it wears quickly. Moreover, because it is heavily loaded, it tends to break out from the body of the floor cutter bit. This is attributable not only to the fact that the floor cutter plate has an inadequate support area, but also because of the considerable wear of the underneath side of the floor cutter bit close behind the floor cutting edge. This wearing process occurs not only during the working movement of the floor cutter bit, but also during the return movement when the cutting does not occur. This wear during the return movement is particularly troublesome when the pivotal movement of the floor cutter bit, into, and out of, its working position is not positively controlled.
With the known type of floor cutter bit, the area of the underneath surface of the bit which is worn reaches as far as the rear soldered joint holding the floor cutter plate within the body of the floor cutter bit. As solder is much softer than the hard metal of the floor cutter plate, this soldered joint obviously wears much quicker than the floor cutter plate. Eventually, this loosens the fixing of the floor cutter plate; and, in an extreme case, the floor cutter plate may even drop out of its aperture. This effect is known as "washing-out".
Washing-out also affects the coal-face cutter plate, but not to the same extent, as the coal-face cutter plate cuts mainly coal and not hard rock. However, as the coal-face cutter plate does extend to the base of the floor cutter bit, at least the lowest portion thereof can engage rock in the floor of a mine working, so a certain degree of washing-out can occur, at least in this lower region of the coal-face cutter plate.
Another disadvantage of the known type of floor cutter bit is that a hard metal pin has to be provided between the floor cutter plate and the coal-face cutter plate, and this leads to high production costs.
The aim of the invention is to provide a floor cutter bit which does not suffer from these disadvantages.